This invention relates generally to filtration apparatus and, more particularly, to apparatus comprising at least one microporous member cooperatively positioned relative to a tubular member to effect removal of particles suspended or dissolved in a fluid medium.
The present invention is particularly useful as a pre-ultrafilter in a desalinization system employing a reverse osmosis membrane module. In systems of this type, seawater is passed, under pressure, through a semipermeable membrane with the desalinized water or permeate being recovered on the opposite side of the membrane. The dissolved salts are separated from the seawater and remain on the influent side of the membrane. A reverse osmosis desalinizaton system of the foregoing type is described in greater detail in copending U.S. patent application, Ser. No. 539,510, filed Jan. 8, 1975, entitled REVERSE OSMOSIS APPARATUS, and assigned to the same assignee as the present application. The aforementioned Application, Ser. No. 539,510, is hereby incorporated herein by this reference and made part of this disclosure.
The use of a pre-filter, especially a pre-ultrafilter, in a reverse osmosis seawater desalinization system is particularly important due to the present of proteinaceous matter in the seawater. If no pre-filter were employed this proteinaceous matter would become trapped on the semipermeable membrane, thus coating the membrane and reducing the efficiency of the system.
As a result, most reverse osmosis systems employ a pre-filter of some type, preferably a pre-ultrafilter. Of those pre-filters employed, the most common are diatomaceous earths, sand filters and cartridge type filters. The most common ultrafilter used employs cellulose acetate as the filtering media. This type of ultrafilter has several disadvantages for use in a reverse osmosis system. The cellulose acetate filter media requires some structural support due to its limited thickness and inherent weakness. As such, special mounting fixtures or hardware are required to incorporate such ultrafilters into conventional reverse osmosis systems. This hardware generally differs from the components used for the reverse osmosis membrane module thus requiring the stocking of many different non-interchangeable parts and thereby increasing the overall cost of the system.
Additionally, the ultrafiltration systems heretofore employed, especially those employing cellulose acetate, require that the filter media be kept moist at all times. Should, for any reason, the filter media be allowed to dehydrate, its filtering properties become severly reduced requiring immediate replacement. Not only does this necessitate the use of elaborate means to insure that the filter media will not dehydrate, but operation in such a constantly moist environment provides an ideal medium for bacterial growth. Since, it is well known that ultrafiltration media heretofore employed, especially cellulose acetate, are subject to bacterial attack, the life expectancy of these ultrafilters is limited.
Ultrafiltration apparatus heretofore employed suffer from the additional disadvantage of not being totally solvent resistant. Since, from time to time, solvents do enter the system, this serves to further reduce the life expectancy of such filter assemblies.
The filtration apparatus of the present invention may also be employed in a number of other filtration systems including, for example, use in connection with known electropainting systems. In these systems, metal parts to be painted are electrically charged and chemically treated to insure better adhesion prior to immersion in paint tanks where electrically charged resin and pigment solids are deposited on their surfaces. The part is then rinsed in a water rinse tank where excess resin and pigment are removed. The rinse water is then passed through an ultrafilter to recover any excess resin and pigment contained therein and then reused.
Additionally, the filtration apparatus of the present invention may successfully be utilized as an ultrafilter medium for separating protein from cheese whey prior to disposal of the processed whey. The presence of this proteinaceous matter in cheese whey pollutes the environment when disposed of in surroundng bodies of water.
Ultrafiltration has also been employed recently in the fractionation of blood. The apparatus of the instant invention is readily adaptable for use in such systems as well.
Against the foregoing background, it is a primary objective of the present invention to provide improved filtration apparatus comprising at least one microporous member and a support for said member provided in the form of tubular member.
It is another object of the present invention to provide improved filtration apparatus which maintains its stability and effectiveness over a relatively long period of use and which is relatively inexpensive to fabricate.